HDU - 2612 M - Find a way BFS

链接 http://acm.hdu.edu.cn/showproblem.php?pid=2612

题目描述

Pass a year learning in Hangzhou, yifenfei arrival hometown Ningbo at finally. Leave Ningbo one year, yifenfei have many people to meet. Especially a good friend Merceki.
Yifenfei’s home is at the countryside, but Merceki’s home is in the center of city. So yifenfei made arrangements with Merceki to meet at a KFC. There are many KFC in Ningbo, they want to choose one that let the total time to it be most smallest.
Now give you a Ningbo map, Both yifenfei and Merceki can move up, down ,left, right to the adjacent road by cost 11 minutes.

输入

The input contains multiple test cases.
Each test case include, first two integers n, m. (2<=n,m<=200).
Next n lines, each line included m character.
‘Y’ express yifenfei initial position.
‘M’ express Merceki initial position.
‘#’ forbid road;
‘.’ Road.
‘@’ KCF

输出

For each test case output the minimum total time that both yifenfei and Merceki to arrival one of KFC.You may sure there is always have a KFC that can let them meet.

样例输入

4 4
Y.#@
....
.#..
@..M
4 4
Y.#@
....
.#..
@#.M
5 5
Y..@.
.#...
.#...
@..M.
#...#

样例输出

66
88
66

直接BFS模拟即可

#include<bits/stdc++.h>


#define REP(i,j,k) for(int i=j; i<k; i++)

using namespace std;
constexpr int MAX = 0x3f3f3f3f;
int main(){
    // freopen("in.dat", "r", stdin);
    int n,m;
    int dir[4][2] = {{0,-1}, {-1, 0}, {1, 0}, {0,1}};
    while(cin>>n>>m){
        vector<string> maze(n);
        using pii=pair<int, int>;
        vector<vector<vector<int>>> ans(n, vector<vector<int>>(m, vector<int>{MAX,MAX}));
        REP(i,0,n) cin>>maze[i];
        queue<pii> que;
        auto valid = [&](int x, int y){
            return x>=0&&y>=0&&x<n&&y<m&&maze[x][y]!='#';
        };
        REP(i,0,n)
        REP(j,0,m)
        if(maze[i][j]=='Y'){
            que.push({i*10000+j, 0});
            ans[i][j][0]=0;
        }
        else if(maze[i][j]=='M'){
            que.push({i*10000+j, 1});
            ans[i][j][1]=0;
        }
        int x, y;
        while(!que.empty()){
            auto e = que.front();
            que.pop();
            for(int i=0; i<4; i++){
                x = e.first/10000 + dir[i][0];
                y = e.first%10000 + dir[i][1];
                if(valid(x, y)&&ans[x][y][e.second]==MAX){
                    que.push({x*10000+y, e.second});
                    ans[x][y][e.second] = ans[e.first/10000][e.first%10000][e.second]+1;
                }
            }
        }
        int res = MAX;
        REP(i,0,n)
        REP(j,0,m)
            if(maze[i][j]=='@')
                res = min(res, ans[i][j][0]+ans[i][j][1]);
        cout<<res*11<<endl;
    }   
    return 0;
}